Abstract: The developing process of expansive soil fissure is logged in the state of deferent water content by the method of field digital imaging.Based on the software of MATLAB,the relationship of field expansive soil fissure ratio and water content is measured through the way of two-value pixels.And the software,which is programmed with the language of AutoLISP,is used to dispose the fractal dimension of fissure.The compute results show that the ratio and fractal dimension of fissure has a linear correlation with water content.The variation of fissure ratio and fractal dimension can reflect the expansive and shrink characteristic of expansive soil.Both the two methods can depict and analyze the surface fissure of field expansive soil,which is effect to the study on fissure behavior.